20 years of US nuclear stockpile stewardship fuels materials research
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20 years of US nuclear stockpile stewardship fuels materials research https://wci.llnl.gov/science/stockpile-stewardship-program
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wenty years ago the US National Nuclear Safety Administration (NNSA) established the Stockpile Stewardship Program (SSP) to keep the country’s few thousand nuclear weapons stockpile safe and reliable. With the end of the Cold War, President George H. W. Bush had announced that the United States would stop developing new nuclear weapons and conducting nuclear explosive tests. The program’s goal was to use innovative experiments and advanced computer models to study the aging of weapon materials and parts, assess and predict weapon performance, and redesign and replace components as needed. During its 20-year lifetime, the USD$6 billion program has in particular pushed the borders of materials science and engineering and computational methods. It has led to new, world-class nuclear weapons research and production facilities. And it has driven collaborations between experts spanning disciplines such as materials science, condensedmatter physics, and computer science. “The nuclear security enterprise is pushing frontiers in computational
science, experiments, and theories,” said NNSA Chief Scientist Dimitri Kusnezov in a news release. “The labs have developed new techniques for understanding the dynamic behavior of materials. Looking ahead, nuclear security will continue to shape the conversation in areas including next-generation exascale computing, advanced manufacturing, and materials science.” Work supported by the SSP is largely centered at Lawrence Livermore, Los Alamos, and Sandia National Laboratories, and has resulted in cutting-edge materials research that also finds applications in industry and academia, says Raymond Jeanloz, professor of astronomy at the University of California–Berkeley, who studies materials properties at high pressures. “These labs have been at the forefront of developing new materials technologies, systems, and experimental techniques, which end up having vastly broad applications,” he says. In a typical nuclear weapon, chemical explosives are detonated to produce shock waves that induce a symmetrical implosion and compression of fissile plutonium
or uranium. This produces a fission chain reaction that releases energy, or, in the case of a hydrogen bomb, ignites a secondary fusion reaction. Nuclear weapons are built of thousands of components containing several classes of materials: fissile uranium and plutonium, metals, organic explosives, plastics, and ceramics. To meet the SSP’s challenge, researchers assess every part of the existing nuclear arsenal annually. They use materials science theory, modeling, smallscale experiments, and large integrated experiments to understand the behavior of materials in normal, abnormal, and hostile environments. They analyze weapon components using destructive methods along with statistical sampling and highresolution electron microscopy, as well as nondestructive techniques such as radiography and ultrasonic imaging.
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